Wafer carriers have been used for many years in the electronic arts, particularly the semiconductor arts, to support wafers during processing. Typical wafer carriers are described, for example, in U.S. Pat. Nos. 4,355,974, 4,256,229, 4,515,104, 3,678,893, 3,534,862, 4,023,691, and 3,610,613 which are incorporated herein by reference. Quartz is a common construction material for wafer carriers that are intended for to high temperature processes. Other materials are also used.
A problem with processing electronic wafers is that defects or non-uniformities are introduced into the wafers during loading, unloading and processing in the carriers. For example, edge chipping may occur, or wafers may become stuck in the carriers, or dislocations may be created in the wafers due to carrier induced stresses, or process gas flow may be perturbed so as to introduce non-uniformities in properties across a wafer or from wafer to wafer. Often, these defects are so small as to escape immediate detection or of a nature to be invisible to the unaided eye, and only reveal themselves in the form of defective devices or circuits or unexpected wafer fracture or "out-of-spec" properties or the like, so that overall manufacturing yield is reduced. As wafers become larger and more expensive, these problems have greater impact on the manufacturing process.
Previous attempts to reduce wafer defect formation and non-uniformities have involved placing the wafers in carriers where they are supported so as to have a slight angle to the vertical. Such expedient is described in U.S. Pat. Nos. 4,355,974 and 4,256,229. While this arrangement may insure uniform wafer spacing it does little to assist in reducing edge chipping which, among other things, is caused by contact between the wafer carrier and the wafer corners where the flat faces of the wafers and the wafer edges join. It has been typical to use V-shaped, or concave-shaped or flat-bottomed slots for supporting the wafer edges. These prior art arrangements substantially increase the chances of edge chipping at the wafer corners. Thus, a need continues to exist for improved wafer carriers that reduce or eliminate edge chipping and that avoid other non-uniformity and/or defect problems often encountered with electronic wafers, especially semiconductor wafers.